I would estimate that it was when EP3 was introduced for paper, and C41 for film, but the conversion to E6 came later. All Japanese companies abandoned Kodachrome type processes in the mid 70s or 80s. They moved to E6.

Agfa introduced a new paper and process in the midst of the Kodak conversion to EP3. Then they moved to EP3, so this process and paper were quite short lived.

PE